Contoh praktikum 7 SA read_graph

#include<iostream.h>
#include<stdlib.h>
#define MAX 20
#define INFINITY 9999
class dijkstra
{
private:
int n;
int graph[MAX][MAX];
int colour[MAX];
int start;
int distance[MAX];
int predecessor[MAX];
enum {green,yellow,red};
public:
void read_graph();
void initialize();
int select_min_distance_lable();
void update(int);
void output();
void function();

};
void dijkstra::read_graph()
{
cout<<"Enter the no. of nodes in the graph ::";
cin>>n;
cout<<"Enter the adjacency matrix for the graph ::\n";
int i,j;
for(i=1;i<=n;i++)
for(j=1;j<=n;j++)
cin>>graph[i][j];
for(i=1;i<=n;i++)
colour[i]=green;
cout<<"Enter the start vertex ::";
cin>>start;
}
void dijkstra::initialize()
{
for(int i=1;i<=n;i++)
{
if(i==start)
distance[i]=0;
else
distance[i]=INFINITY;
}
for(int j=1;j<=n;j++)
{
if(graph[start][j]!=0)
predecessor[j]=start;
else
predecessor[j]=0;
}
}
int dijkstra::select_min_distance_lable()

{
int min=INFINITY;
int p=0;
for(int i=1;i<=n;i++)
{
if(colour[i]==green)
{
if(min>=distance[i])
{
min=distance[i];
p=i;
}
}
}
return p;
}
void dijkstra::update(int p) // p is a yellow colour node
{
cout<<"\nupdated distances are ::\n";
for(int i=1;i<=n;i++)
{
if(colour[i]==green)
{
if(graph[p][i]!=0)
{
if(distance[i]>graph[p][i]+distance[p])
{
distance[i]=graph[p][i]+distance[p];
predecessor[i]=p;
}
}
}
cout<<distance[i]<<'\t';
}
}
void dijkstra::output()

{
cout<<"****** The final paths and the distacnes are ******\n\n";
for(int i=1;i<=n;i++)
{
if(predecessor[i]==0 && i!=start)
{
cout<<"path does not exists between "<<i<<" and the
start vertex "
<<start<<endl;
exit(1);
}
cout<<"path for node “<<i<<” is ::\n";
int j=i;
int array[MAX];
int l=0;
while(predecessor[j]!=0)
{
array[++l]=predecessor[j];
j=predecessor[j];
}
for(int k=l;k>=1;k=-k)
cout<<array[k]<<"->";
cout<<i<<endl;
cout<<"distance is "<<distance[i]<<endl<<endl<<endl;
}
}
void dijkstra::function()
{
cout<<"\n*****************************************************************
*****\n";
cout<<"This program is to implement dijkstra’s algorithm using colour
codes \n";
cout<<"*******************************************************************

***\n\n";
read_graph();
initialize();
//repeate until all nodes become red
int flag=0;
int i;
cout<<"\n\n******** The working of the algorithm is **********\n\n";
for(i=1;i<=n;i++)
if(colour[i]!=red)
flag=1;
cout<<"The initial distances are ::\n";
for(i=1;i<=n;i++)
cout<<distance[i]<<'\t';
cout<<endl;
while(flag)
{
int p=select_min_distance_lable();
cout<<"\nThe min distance lable that is coloured yellow is "<<p;
colour[p]=yellow;
update(p);
cout<<"\nnode "<<p<<" is coloured red "<<endl;
colour[p]=red;
flag=0;
for(i=1;i<=n;i++)
if(colour[i]!=red)
flag=1;
cout<<endl<<endl<<endl;
}
output();
}

void main()
{
dijkstra d;
d.function();
}